1. Field of the Invention
The present invention relates to an electronic control system for a motor vehicle in which a plurality of controllers are connected by serial communication lines.
2. Description of the Prior Art
In recent years, microcomputers have come to be installed on motor vehicles such as automobiles. The microcomputers have been used in, for example, an engine control, a transmission control and a brake control, and have brought forth the rapid progress of control functions.
Subsequently, such a system wherein the plurality of microcomputers perform the individual controls independently has developed into a system wherein a plurality of microcomputers are coupled by a serial channel so as to organize a network and to interchange required data items through serial transmission. Byway of example, the official gazette of Japanese Patent Application Laid-open No. 237895/1987 discloses a technique wherein a plurality of controllers are connected by a serial data link, and even when data items from sensors are simultaneously required in the individual controllers, they are transferred through a single communication line, thereby to reduce the number of wiring lines in an automobile.
However, with the independent distributed processing system wherein the plurality of microcomputers are merely coupled by the communication network, the adjustments of tasks among the microcomputers are difficult, and the overhead of each microcomputer in case of communication increases, granted that the sharing of data and the reduction of the number of wiring lines can be achieved.
Further, regarding a system wherein computers of different capabilities are coexistent, etc., there are the problems that the throughput of the whole system might lower and that the integration of the whole control system is difficult.